Introduction

The inflamed joints in rheumatoid arthritis patients are ideally suited for gene therapy applications to acquire local production of potent anti-inflammatory biologics. The need for precise and absolute targeting as for treating cancer is not necessary in rheumatoid arthritis. However, the challenge is to obtain long-term transgene expression. For this purpose we used in this study HIV-based lentiviruses (LV) for the stable transduction of the murine synovium.

Methods

The coding sequence of murine interleukin-1 receptor antagonist (IL-1Ra) was inserted into the pRRLcpptpgkmcspreSsin transfer vector (self-inactivating vector was a gift from D Trono, Geneva, Switzerland) behind the phosphoglycerate kinase-promoter. Vesicular stomatitis virus G envelope pseudotyped lentiviruses were produced by cotransfection of 293T-cells [1]. Recombinant lentiviruses were purified and titres were determined using the p24 ELISA (Murex HIV Antigen MAB, Abbott). Lentiviruses encoding for firefly luciferase (Luc) were used for control. The lentiviruses were injected intra-articularly into the murine knee joint. Synovial explants were taken to measure the luciferase activity using a luminometer. Mice immunized against bovine collagen-type II received an intra-articularly injection of lentiviruses 1 day after the antigen booster but without any visual signs of collagen-induced arthritis.

Results

Naïve C57Bl/6 mice were injected with 300 ng (p24 value) of LV-Luc into the knee joint. The Luc activity in the synovial biopsies increased steadily until day 7 and remained at this level until the end of the experiment (day 21 after injection). Next we injected the same amount of LV-mIL-1Ra and LV-Luc into the right knee joint of collagen-type II immunized mice just before onset of arthritis. At day 31 after immunization all mice in the LV-IL-1Ra and LV-Luc-treated groups developed clinical signs of severe arthritis in the paws. However, macroscopic examination of the injected knees showed a significant reduction in joint inflammation in all mice of the LV-mIL-1Ra group (arbitrary score [0–3] 0.55 ± 0.37) as compared with the LV-Luc-treated mice (score 1.55 ± 0.53). Microscopic evaluation confirmed the marked reduction in joint inflammation. Furthermore, the joint that received LV-mIL-1Ra showed a marked reduction in bone destruction whereas the extent of cartilage destruction was comparable with the LV-Luc-treated knees during collagen-induced arthritis.

Conclusion

We show for the first time that lentiviral-mediated local overexpression of IL-1Ra had a pronounced effect on the development of collagen-induced arthritis in that particular knee joint. No protective effect was observed on the ipsilateral or contralateral paws as we have demonstrated previously for IL-1Ra gene transfer using adenoviral vectors [2, 3]. The lentiviral transduction of the synovium seems feasible and efficacious for treatment of arthritis.